This invention relates to processes for the preparation of alpha-diketones.
Alpha-diketones are valuable intermediates for pharmaceutical products, dyestuffs and perfumes and therefore a variety of methods for preparing such compounds have previously been suggested and employed. For example, alpha-diketones have been prepared by nitrosation of appropriate ketone derivatives followed by hydrolysis as illustrated by equations (1) and (2). V. Peckman, Ber., Vol. 21, Page 1411 (1888); Vol. 24, page 3954 (1891). ##STR1##
Various oxidation reactions, as exemplified by equations (3) through (9), have also been suggested. ##STR2##
In addition, preparation of alpha-diketones by hydrolysis of acetylene derivatives and epoxy derivatives, as exemplified by equations (10) and (11) respectively, has been reported. ##STR3##
Finally, condensation reactions between alpha-hydroxyl ketones and aldehydes have also been reported. Such reactions are exemplified by equations (12) and (13). ##STR4##
Unfortunately, however, the various known methods of synthesizing alpha-diketones are often commercially unsatisfactory by virtue of low yields; high energy requirements; slow reaction rates; limited availability, chemical instability, or high cost of the required reactants or catalyst; complex reaction procedures; complex purification procedures; toxicity of reactants, catalyst or by-products; etc.
It is therefore desirable to provide a process for preparing alpha-diketones in high yield (e.g., 50 to 80 percent or more) from readily available, stable and economical raw materials via a simple process and without the need for (or production of) highly toxic raw materials, catalyst or intermediates.